Alternate Sorcerers[]
EoM-Style Sorcerer[]
This variant sorcerer is drastically different from the standard. Essentially, it uses the Mage class from the Elements of Magic 3rd-party sourcebook.
Elements of Magic is a drastically different, more freeform magic system than the standard D&D Vancian-style magic system. EoM casters learn "spell lists," which are seeds from which both freeform and "signature" spells are cast. They are also MP-based casters, rather than using spell slots.
The idea behind this change is that a sorcerer, much more than a wizard, has a direct connection through his blood and his will to the very essence of magic. This connection allows him to draw upon the power of magic directly and manipulate it to his whim rather than according to the formulae of some long-dead wizard. EoM sorcerers would become very different from wizards, acting as the intuitive artist to the wizard's logical engineer.
Tome of Battle Sorcerer[]
In the Tome of Battle, there's an alternate version of the Swordsage class that allows the Swordsage to take arcane spells in place of some of his maneuvers. This variant of the sorcerer would follow the same basic rule: he would have a certain (small) number of spells known and a number of spells ready. The sorcerer would be able to cast these spells once per encounter before taking an action to recover them, and would be able to change out his prepared selection between encounters.
It is likely that this approach would render the sorcerer considerably more powerful than it already is. This variant hasn't been playtested, but seems a worthwhile experiment, and would provide a more marked difference from the wizard than the current sorcerer.